Glossary
Carbon dioxide equivalent (CO₂e)
Carbon dioxide equivalent (CO₂e) is a standard unit for measuring carbon footprints. It expresses the effect of each different greenhouse gas in terms of the amount of CO2 that would create the same amount of warming. This allows multiple gases to be compared on an equal footing.
The term CO₂e is widely used in discussions about climate change and greenhouse gas emissions. It is premised on the capability of greenhouse gases to trap heat in the atmosphere, also known as their global warming potential (GWP). Predominantly, the gas under comparison is carbon dioxide (CO₂) as it is the most emitted greenhouse gas by human activities and serves as a reference point in the CO₂e concept.
When discussing CO₂e, the conversation often revolves around how these greenhouse gases contribute to climate change over a certain period, typically 100 years. Some greenhouse gases are more potent than CO₂ but may not last as long in the atmosphere. Conversely, others may be less potent but persist for longer periods. As such, CO₂e is calculated by multiplying the amount of the gas by its associated GWP.
The use of the CO₂e unit provides a common platform, enabling comparisons involving various greenhouse gases. For instance, methane (CH4) is a greenhouse gas with a GWP 25 times greater than CO₂ over a 100-year span. Hence, emitting 1 tonne of methane into the atmosphere is equivalent to emitting 25 tonnes of CO₂, thus represented as 25 CO₂e.
Understanding CO₂e is essential in the renewable energy sector and carbon accounting, as it provides a more comprehensive viewpoint on the emissions’ effect. By adopting CO₂e as a measurement unit, organizations can account for all greenhouse gases emissions related to their activities, facilitating monitoring, reporting, and efforts to reduce their carbon footprint.